Conventional Chinese medical treatments, such as acupuncture and tuina, which achieve efficacy by stimulating acupuncture points of the human body, improve as a result of technological advancement, thereby developing electrotherapy devices which stimulate acupuncture points of the human body by an output voltage to therefore achieve a known level of efficacy and provide users with an alternative to conventional Chinese medical treatments.
Electrotherapy devices come in three types: low-frequency (below 1 kHz) electrotherapy devices, medium-frequency (1 kHz˜100kHz) electrotherapy devices, and high-frequency (above 100 kHz) electrotherapy devices. Low-frequency and medium-frequency electrotherapy devices are commercially available. For instance, low-frequency electrotherapy devices operate by Transcutaneous Electrical Nerve Stimulation (TENS) and Electrical Muscle Stimulation (EMS), whereas medium-frequency electrotherapy devices work with a vector interference electrotherapy apparatus and a medium-frequency modulated electrotherapy device.
Electrotherapy effectuates stimulation of the human body's nerves, muscles, and cells with appropriate electrical signals (which depend on parameters, such as voltage level, frequency, duty cycle, and stimulation duration.) Electrotherapy is a therapeutic technique derived from an acupuncture theory based on a combination of rehabilitation medical engineering and traditional Chinese medicine. According to traditional Chinese medicine and rehabilitation theory, acupuncture points lie beneath the skin of the human body and have a specific depth and scope.
Electrotherapy devices pass output signals to the human body through the human skin. From the perspective of electricity, impedance features of the human skin originate in “capacitive impedance.” Hence, equivalent features of the human skin are quite similar to that of a “capacitor,” and therefore they can be described with the following mathematical equations: Xc=1/ωc, ω=2πf, where f denotes frequency, and Xc denotes capacitive impedance, wherein frequency is inversely proportional to capacitive impedance. Therefore, the higher the frequency of an output signal of an electrotherapy device, the lower the impedance of the human skin, such that the output signal can reach the human body's tissues. Conversely, the lower the frequency of the output signal of the electrotherapy device, the higher the impedance of the human skin, such that the output signal acts on the surface of the skin rather than goes deep into the human body's tissues.
Therefore, the effective depth of electrotherapy devices depends on the frequency of the output signal. During their electrotherapy session, conventional electrotherapy devices always make their carrier waves operate at a fixed frequency. For “a plurality of” outputs of vector interference electrotherapy devices to produce interference effect (for preventing the human body's self-adaptation to an output voltage with a fixed frequency), it is necessary that the frequencies of its two outputs approximate to each other. Therefore, from the perspective of effective depth analysis, the electrotherapy effect results from a change in a small range of frequencies. After use for a while, although it postpones the human body's self-adaptation to the output voltage, the human body's self-adaptation will occur anyway.
Therefore, conventional electrotherapy devices are subject to limits because of the design of carrier wave frequency. As a result, during their electrotherapy session, they are confined to a specific effective depth (the depth below the skin) and therefore are not changeable, and in consequence areas other than the acting area cannot be fully stimulated. For instance, since their carrier wave frequency is fixed, conventional electrotherapy devices are subject to limits in both effective depth and scope. As a result, in the course of electrotherapy, stimulation is restricted to trigger points or acupuncture points of a specific depth, and in consequence stimulation cannot fully affect trigger points or acupuncture points which are nearby and have different depths. In another aspect, since electrotherapy produces stimulation effect by an output voltage with a frequency, as described above, from the perspective of the human body, after identical frequencies or similar frequencies have persisted for a period of time, the human body undergoes self-adaptation and thereby adapts to the frequency, and in consequence the stimulation effect of electrotherapy dwindles greatly. To circumvent the human body's adaptation to a fixed pulse frequency, vector interference electrotherapy devices adopt mutual interference of two frequencies to block the self-adaptation mechanism of the human body. However, vector interference electrotherapy devices are still confronted with problems, for example, the human body's adaptation to the effective depth, acting scope, and long use, as well as drawbacks, for example, the two outputs cause the electrotherapy devices to incur high manufacturing costs and require high power consumption.
Moreover, conventional electrotherapy devices have further drawbacks. For instance, in the course of generating an output voltage, the switching speed is so low that the waveform of the pulse generated is inconspicuous, thereby compromising the effect of electrical stimulation. In addition, conventional electrotherapy devices control pulse strength (voltage level) by the adjustment performed with a built-in variable resistor of the switching unit, and in consequence it is difficult for electrotherapy devices to perform adjustment for the sake of fine variations, thereby rendering it difficult for users to perform adjustment in order to attain an appropriate electrical stimulation level (i.e., voltage level). Furthermore, the switching unit of conventional electrotherapy devices is likely to generate residual heat and therefore the operating temperature of the electrotherapy devices is usually high. Therefore, it is important to overcome the aforesaid drawbacks of the conventional electrotherapy devices.